Characterization of senescence of culture-expanded human adipose-derived mesenchymal stem cells

Background and Objectives: Adipose-derived mesenchymal stem cells (ADSCs) are promising candidates in regenerative medicine. The need for in vitro propagation to obtain therapeutic quantities of the cells imposes a risk of impaired functionality due to cellular senescence. The aim of the study was to analyze in vitro senescence of previously cryopreserved human ADSCs subjected to serial passages in cell culture. Methods and Results: ADSC cultures from 8 donors were cultivated until proliferation arrest was reached. A gradual decline of ADSC fitness was observed by altered cell morphology, loss of proliferative, clonogenic and differentiation abilities and increased β-galactosidase expression all of which occurred in a donor-specific manner. Relative telomere length (RTL) analysis revealed that only three tested cultures encountered replicative senescence. The presence of two ADSC subsets with significantly different RTL and cell size was discovered. The heterogeneity of ADSC cultures was supported by the intermittent nature of aging seen in tested samples. Conclusions: We conclude that the onset of in vitro senescence of ADSCs is a strongly donor-specific process which is complicated by the intricate dynamics of cell subsets present in ADSC population. This complexity needs to be carefully considered when elaborating protocols for personalized cellular therapy.publishersversionPeer reviewe

Cellular Immunogenicity of Novel Gene Immunogens in Mice Monitored by in Vivo Imaging

The efficient cell-mediated immune response clears cells expressing deoxyribonucleic acid (DNA) immunogens, but there are no methods to monitor this in vivo. We hypothesized that immune-mediated clearance can be monitored in vivo if DNA immunogens are coexpressed with reporter(s). To test this, we designed genes encoding human immunodeficiency virus 1 (HIV-1) reverse transcriptase (RT) fused via its N- or C-terminus to 30–amino acid-long Gly-Ala-repeat of Epstein-Barr virus nuclear antigen 1 or via the N-terminus to the transport signal of invariant chain/Ii or inserted between the cytoplasmic and luminal domains of lysosome-associated membrane protein I (LAMP). DNA immunogens mixed with luciferase gene were injected into BALB/c mice with subsequent electroporation. Reporter expression seen as luminescence was monitored by in vivo imaging. When luminescence faded, mice were sacrificed, and their splenocytes were stimulated with RT-derived antigens. Fading of luminescence correlated with the RT-specific secretion of interferon-γ and interleukin-2. Both immune and in vivo imaging techniques concordantly demonstrated an enhanced immunogenicity of RT-LAMP and of the N-terminal Gly-Ala-RT fusion genes. In vivo imaging performed as an animal-sparing method to estimate the overall performance of DNA immunogens, predicting it early in the experiment. So far, in vivo imaging cannot be a substitute for conventional immune assays, but it is supplementary to them. Further experiments are needed to identify which arms of cellular immune response in vivo imaging monitors best